Incorporation of organic soil ameliorants to boost productivity of sandy soils in the medium to high rainfall zones of the wheatbelt of Western Australia.

Project Start Date: April 2020

Project End Date: April 2023

Project Funding: GRDC

Project Lead: Corrigin Farm Improvement Group

Project Collaborators: Facey Group, West Midlands Group.

Project Focus:

Approximately 35% of the soils in the Western Region are made up of sandy soils, including deep sands and sandy duplexes. The sand component of these soil profiles is inherently infertile, has low organic matter levels, low water holding capacity, can have water repellence and compaction issues. In order to increase the productivity of these ‘gutless’ sandy soils, it has become relatively common practice for growers to use soil amelioration methods such as spading, plozza ploughing and deep ripping to alleviate soil constraints such as compaction and non-wetting. While this can be of benefit to physical soil constraints, the constraint of low soil fertility is currently not being addressed.

There is increase interest in the medium to high rainfall zones (MRZ & HRZ) of the WA Wheatbelt to find ways of increasing the fertility of these ‘gutless’ soils through the application of organic ameliorants (e.g. under-grade hay, straw, manure). It is hoped that this approach may increase the organic matter content of the soil to increase soil nutrient supply and water holding capacity of the soil. Through this approach it is hypothesized that this will lead to an increase in grain yield and profitability for the growers.

There is the need to re-evaluate this approach of applying organic amendments and its integration with current soil amelioration methods. Many studies in the past have looked at the yield benefit of applying organic amendments but have been hampered in adoption by practical means of application and incorporation. The widespread adoption of soil amelioration methods now that can incorporate organic amendments to a possible depth of 30 cm necessitates the revisiting of the practice of applying organic amendments to improve soil fertility.

Project information:

 This grower scale demonstration trial is to being conducted over three seasons (2020-2022).

The selection for the site was based on the requirement to locate a poor performing sandy paddock that has a history of lower than average yields. The three organic ameliorants selected for incorporation included chicken manure, straw and hay, applied at two different rates of 10t/ha & 5t/ha for manure and 6t/ha & 3t/ha for hay and straw prior to the commencement of the trial in 2020.  The higher rates of organic ameliorants were incorporated into the soil using a Mouldboard plough, whilst the lower rates were incorporated by speed tiller with the exception of the low rate hay which was incorporated by Mouldboard plough. A grower practice of Mouldboarding (with no addition of organic ameliorant) has also been used as a benchmarking treatment along with a nil control. For the purpose of also gauging yield response to other common soil amelioration practice, an application of clay incorporated by speed tiller has been included for comparison in this experiment.

A pretrial soil analysis was conducted in 2020 to provide a baseline for measuring improvements in soil nutrition and health as well as a full analysis of the mineral and organic composition of the manure and plants. In season recording each season includes plant emergence numbers, plant growth and biomass, weed counts and grain yield and quality, and will form the basis for conducting statistical and economic analysis over the three-year trial period.     

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